A state of being in which a hangover is so unpleasant that it renders the person unable to walk in a normal fashion. The person's stride is slow, erratic, and languid--thus resembling reanimated fleshless dead. If one goes "skeletal" they will undoubtedly lose an entire day to their hangover and will not be able to perform basic tasks.

The noun form is "skeletor". A skeletor typically spends his entire day watching TV from a couch while wearing sunglasses. He will move only to vomit.

~20 year old shuffles into kitchen on New Year's Day~
"I want to shit, but I know if I do, I'll throw up."
"John, you went skeletal dude."

~Two guys at party~
"Im on my sixth shot and we've only been here a half hour."
"Sam, you're gonna be goin skeletal by midnight."